It is currently known to have buildings up for sale locked with a lock box storing the key to the building. The lock box may be attached to the door or a structure adjacent to the building. The lock box includes a cover, latch operable to release the cover, and an interface operable to receive a code. Upon input of the proper code, the cover will open so as to provide access to the key which can then be used to unlock the door and access the building.
It is also known for homes to have a more advanced lock system. An example of an advanced lock system is a lock with an electronic pad wherein the user can enter in an access code and electronically disengage the lock and access the building. However, such electronic systems are expensive and may be prone to being inoperable when there is an electric outage. Furthermore, a conventional key lock may present problems where the owner has lost the key or locked himself out of the building by leaving the key in the locked building.
A combination lock such as a thumb wheel lock may provide an economically feasible way to unlock a door. Current combination locks are operable to lock and unlock a door. However, such combination locks create a positive lock, meaning when used in a door the combination lock will interfere with the operation of the opposing doorknob. Thus a user may be trapped inside of the building when the door is closed. Accordingly it is desirable to have a doorknob with a locking device whereby the user does not have to retain a key but can gain access using a combination or code. It is also desirable to have a door knob that provides access using a combination or code that is relatively inexpensive compared to the door knob with the electronic locking device referenced above. Additionally, it is desirable to having a door knob having a locking device that allows a user to engage the latch mechanism from within the building.